1. Field of the Invention
This invention in general relates to photography and in particular to an adapter by which a self-contained automatic camera can be coupled to an optical viewing device such as an endoscope to photograph an image formed by the eyepiece of the viewing device in a manner whereby an automatic exposure control feature of the camera is preserved.
2. Description of the Prior Art
Photographic cameras of the type which include systems by which exposure of a film is automatically controlled in a predetermined manner are well-known in the prior art. In general, such exposure control systems usually comprise an electromechanical shutter arrangement that is controlled by the output of a scene brightness measuring system in such a way that aperture and/or shutter speed are set in accordance with a film's given speed rating and what the scene brightness measuring system judges the "average" scene brightness to be.
Also well-known to the prior art are optical viewing devices such as microscopes, telescopes, binoculars, and endoscopes--all instruments useful for their ability to permit visualization of details in objects which would otherwise be too distant, small, dim or inaccessible for the unaided eye to see.
Obtaining permanent photographic records of what the eye sees through such optical viewing devices is an established practice having obvious scientific and artistic benefits. Like others, however, this photographic practice requires, among other things, that the image of the object to be photographed be available for observation immediately prior to and preferably during exposure and also must be properly exposed to record important details in the object--particularly in medical applications like endoscopic photography. These requirements are generally difficult to satisfy especially where the camera includes an automatic exposure control system as described above and does not have a reflex viewing arrangement where the image can be observed directly through the camera objective lens.
Consequently, using a camera with automatic exposure control to photograph images formed by such optical viewing devices requires that the automatic exposure control be bypassed or overridden in some way or alternatively be coupled with the viewing device in such a way that the brightness of the image formed by the viewing device can be measured by the brightness measuring system of the camera. The alternative above, while advantageous because it preserves the camera automatic exposure control feature, presents a major problem since the viewing device image is generally hidden from the view of the camera brightness measuring system. This usually comes about because of an offset between the camera objective lens, which is generally optically aligned with the viewing device image, and the optical axis of the camera brightness measuring system. Moreover, unless the camera includes a reflex viewing device, such as those of the single lens reflex or twin reflex lens type camera, the problem becomes aggravated.
Some prior art arrangements for coupling automatic exposure control systems of self-contained cameras with optical viewing devices show arrangements by which some part of the useful light intended for the photographic image is diverted to the photodetector of the camera automatic exposure control system through the use of branched light paths which typically utilize beamsplitters, fiber optic bundles or similar optical elements. Typical of such arrangements are those shown, for example, in U.S. Pat. No. 3,641,898 issued to Ichizo Kawahara on Feb. 15, 1972 and entitled "Electrically Driven Camera For An Endoscope"; U.S. Pat. No. 3,721,170 issued to Bruce K. Johnson on Mar. 20, 1973 and entitled "Apparatus For Adapting A Reflex Camera For Use With A Monocular Microscope"; U.S. Pat. No. 3,292,490 issued to Kenneth M. Moore on Dec. 20, 1966 and entitled "Photographic Equipment"; and U.S. Pat. No. 3,798,665 issued to Vaito K. Eloranta et al. on Mar. 19, 1974 and entitled "Apparatus For Adapting A Reflex Camera To Use With A Binocular Microscope".
Other prior art arrangements show apparatus by which a part of the image light not intended for the photographic image, but representative of the brightness of the viewing device image, is diverted to the camera automatic exposure control system photodetector or light sensing element. Such arrangements are similar to those shown, for example, in U.S. Pat. No. 3,898,678 issued to Vivian K. Walworth on Aug. 5, 1975 and entitled "Camera To Microscope Adapter With Means For Operating An Exposure Control" and U.S. Pat. No. 3,900,858 issued to Mary Conlin McCann et al. on Aug. 19, 1975 and entitled "Camera To Microscope Adapter With Special Optical Element".
None of the known prior art arrangements, however, appear to show means by which a self-contained automatic camera with a non-through-the-lens viewing device can be coupled with an optical viewing device to photograph and view an image formed thereby while making use of the camera's automatic exposure control system. Therefore, the foregoing is a primary object of the present invention. Other objects of the invention will in part be obvious and will in part appear hereinafter. The invention accordingly comprises the apparatus possessing the construction, combination of elements and arrangement of parts which are exemplified in the following detailed disclosure.